Kit Guidance - Windows users should run CLI/Shell as Administrator

[Tosin-88]

Hi Team,

Brilliant work on the prototype kit :)

Small change though to the guidance doc. It should advise Windows users to run command as an administrator otherwise the user will be restricted from running the node package manager

[davidhunter08]

Thanks @Tosin-88.

[vickytnz]

This may be related to #68 though does seem to be more general Windows instructions. The GOV.UK prototype kit doesn't have this as an instruction https://prototype-kit.service.gov.uk/docs/install/requirements-windows so this may need checking with a Windows user first?